This invention relates generally to powder preform consolidation processes, and more particularly to such processes wherein consolidated tantalum powder parts are produced. The use of higher density metals such as tantalum for replacement of copper in the fabrication of explosively formed penetrators (EFP's) and shape charge liners (SCL's) is of considerable interest in the field of ballistic devices. However, certain metallurgical, fabrication and cost related issues currently limit the use of tantalum for task specific ballistic applications.
The conventional fabrication technique for sheet and plate is ingot metallurgy followed by standard thermomechanical metal working practices such as forging and rolling. These fabrication processes, however, produce highly undesirable textured microstructure which yield anisotropic static and dynamic properties over both low and high strain rate regimes. Machining of the tantalum plate or sheet stock to its final EFP or SCL geometry contributes not only to an additional loss of ductility through work hardening mechanisms, but also adds significant cost to the final product.
The role of texture on microstructure development and dynamic mechanical properties has been recognized by a number of investigators (.sup.1-4). Several common metal working practices such as extrusion, rolling and forging have undergone careful scrutiny as methods of producing ballistic grade tantalum. These studies have shown that the presence of a &lt;111&gt; texture orientation improves formability (ductility) of the tantalum metal. However, these thermomechanically oriented processes also cause the tantalum to exhibit an anisotropic mechanical behavior due to the creation of a non-uniform texture. Through orientation distribution function (ODF) analysis forged and rolled tantalum is found to exhibit a pole density of 5X random. This non-uniform texture is known to have deleterious effects on the high-strain rate performance of the EFP which results in both an uneven collapse of the tantalum body upon impact, and the subsequent generation of unpredictable fin configurations.